Rotary pistons, in the nature of encased rotors with radially extending vanes which move in and out of the rotors, depending upon their location within the casing used, for example, as pumps or turbines, are known. One such device is described in U.S. Pat. No. 6,554,596 of Albert and David Patterson issued Apr. 29, 2003, in which the vane movement, in and out of the rotor, is achieved by cam surfaces within the casing which act on both inner and outer edges of the vanes.
Other known constructions of such vane “motors” require centrifugal force, through rotation of the rotor, to force the vanes out.
Problems with such arrangements, if applied to hydraulics, include leakage of fluid between the vanes and consequent inability to effectively and efficiently handle fluids under high pressure. Of necessity, such devices have conventionally been of relatively small size, and, while they have been able to operate at fast speeds, they have been able to move only relatively low volumes of fluid.
It is an object of the present invention to provide a hydraulic pump for liquid or air which will operate efficiently and effectively at medium or high pressures and handle high fluid volumes and high torque at low, medium or high fluid pressure.